Rotary index tables in the form of turning of dividing tables on machine tools have hitherto been employed for establishing and measuring predetermined angular distances, cam tracks and the like.
Turning tables have the advantage that they can be fixed in any desired angular position. However, the brake means which such turning tables are provided with for maintaining the table in a stationary position cannot guarantee absolutely reliable securement of the table in the presence of strong displacement forces.
Dividing tables offer the advantage of being provided with Hirth-type serrations and are therefore able to resist even great displacement forces. On the other hand, dividing tables can only be fixed in predetermined angular positions corresponding to a multiple of the pitch of the Hirth-type serration.
In view of the disadvantages that have to be tolerated in both known table constructions, successive machining of workpieces on the two known types of rotary index tables is often unavoidable in manufacturing technology.
Accordingly, the object underlying the invention was to produce a rotary index table which unites the advantages of the known turning and dividing tables within itself and can therefore be universally employed on machine tools both as a turning and dividing table.
The object underlying the invention is attained by a rotary index table of the type described at the beginning in accordance with German Published patent application No. 1,962,097.
If, for example, predetermined angular distances corresponding to a multiple of the tooth pitch of the Hirth-type serrations are to be established on the rotary index table according to the invention, the table plate can be secured in position on the table housing by the Hirth-type serrations.
If, on the other hand, the table plate is to be rotated through angles which cannot be set by the Hirth-type serrations on the basis of their pitch, the table plate can be secured in position on the table housing by the brake means, once it has been adjusted to the respective angular position. Thus, the table plate can also be secured in any angular position.
It is advisable to electronically control the drive means for adjustment of the table plate through both predetermined turning angles which can be established by the tooth pitch of the Hirth-type serrations and turning angles of any size, so that the angular positions of the table plate that are to be selected successively can be programmed in the controls of the respective machine in advance and then automatically performed.
Electronic control of the drive means for determining measurement values corresponding to angular positions to be selected can be effected by a direct electronic measurement system (rotary inductosyn system) or advantageously by an indirect measurement system (resolver measurement).
The rotary index table according to the invention offers the following adjustment possibilities, assuming that the Hirth-type serrations have a tooth pitch of one degree. In this case, the table plate can be secured in 360 positions with the aid of the Hirth-type serrations. Used as a turning table with a direct and/or indirect electronic measurement system for controlling the drive means, the table plate can in accordance with the resolver power of the measurement system and the electronic machine controls be adjusted to, for instance, 360,000 positions. If, on the other hand, the Hirth-type serrations have a pitch of 0.5.degree., the table plate can be adjusted to 720 positions with the aid of the Hirth-type serrations.
If the rotary index table is used as a dividing table, raising of the table plate from the table housing so as to disengage the Hirth-type serrations for indexing the table plate can be avoided. In this case, it is expedient for the adjustment member for raising and lowering the carrier plate to be in the form of an adjustable wedge which can cooperate suitably with a guide shaft that is guided in the table housing and carries the carrier plate. The construction disclosed constitutes a preferred embodiment of the invention which enables positive guidance of the carrier plate in both of its directions of movement. The toothed ring provided therein enables, in addition to a favorable arrangement of a Hirth-type serration on the table plate, an advantageous drive connection between the table plate and the drive means, if, the toothed ring comprises at its circumference a ring gear which meshes with a drive wheel of the drive means. The ring gear and the drive wheel can be in the form of spur gears which mesh with one another, and the brake means must be designed such that it enables either a decrease in the flank play or absolutely reliable securement of the table plate relative to the table housing, depending on how the rotary index table is to be used.
By the simple structural measure disclosed, the flank play can be reduced and the toothed ring detained, respectively. If, for example, the table plate is to be driven for milling cam tracks, the flank play can be reduced to an advantageous value in the manner disclosed. On the other hand, the flank play can be correspondingly enlarged at short notice if the table plate is to be operated at rapid traverse rate. Finally, the tooth flanks can be brought together under pressure in order to secure the table plate.
In a preferred embodiment of the invention, the drive means and the brake means constitute one component, as disclosed, which is designed such that the drive wheel of the drive means which meshes with the ring gear of the toothed ring on the table plate constitutes at the same time the brake member for securing the ring gear and the table plate, respectively.
A construction which distinguishes itself by way of particular structural simplicity and functional reliability can be obtained by having the ring gear of the toothed ring take the form of a worm gear which meshes with a drive worm of the drive and brake means, said drive worm being adapted to be radially displaced by the brake means in the direction of the worm gear so as to secure the worm gear and the table plate, respectively, and to engage with the flanks of the worm gear under pressure. In this way, any play between the tooth flanks of the worm gear and the threads of the drive worm is eliminated, and the table plate is thereby locked to the table housing in an absolutely reliable manner, provided that the drive worm is free of play in both axial directions. The subject matter of the invention constitutes further advantageous embodiments of the drive and brake means in the form of one component.
Further features and details of the invention are apparent from the following description of a preferred embodiment of a rotary index table according to the invention, as illustrated in the drawings, and also from the patent claims.